Devices for actuating a process valve for use in foodstuffs technology are known in the art, e.g. the control unit distributed by the present applicant for the double-seat valve DELTA DA3+.
Control units or devices for actuating a double-seat valve are disclosed for instance in U.S. Pat. No. 5,435,853.
The known devices for actuating a process valve (for example, a double-seat valve), for use in foodstuffs technology, that has a first cylinder and a second cylinder, have a first control valve having a connector for a line to the first cylinder of the double-seat valve, an intake-air connector and an exhaust-air connector, and have at least one further, or a second, control valve having at least a connector for a line to the second cylinder of the double-seat valve, a connector for an intake-air line and a connector for an exhaust-air line.
In the case of the known devices for actuating a process valve, the exhaust air of the various control valves is taken away collectively, i.e. the exhaust-air lines of the individual control valves are interconnected and have a common outlet into the environment. This can give rise to the disadvantage that the venting of air from one control valve via the common exhaust-air line causes compressed air to come in via another control valve that has connected the exhaust-air line to the cylinder chamber normally actuated by it.
Although, in this position, the exhaust air from the cylinder chamber is intended to escape outwards, the compressed air present in the common exhaust-air line can result in unintentional actuation of the process valve by the control valve that is switched to exhaust ventilation. Unintentional, short-duration opening of one of the valve stems can be effected as a result. This is particularly undesirable in foodstuffs technology, and can constitute a safety-relevant hazard for the quality of the foodstuff, since, for example, contamination of the leakage cavity can occur as a result.
A further resultant disadvantage is that there can be a loss of product, owing to the unintentional lifting motion of one of the valve stems.